The present invention relates to, for example, methods and apparatuses for stamping metal plates for forming separators of fuel cells.
Separators of fuel cells are formed of metal plates. A separator has, at its center, bulging portions, which correspond to a sealing portion and a flow passage for fuel gas or oxidation gas. The bulging portions are typically formed through stamping. The metal plate thus has residual stress after stamping. The residual stress can result in changes in the shape or the size of the metal plate when the metal plate is sheared into a predetermined shape after stamping. This can lower dimensional accuracy.
Japanese Laid-Open Patent Publication No. 2009-255106 discloses a technique for producing an embossed intermediate product. The embossed part is flattened to reduce stress that would otherwise cause warpage of the intermediate product.
Japanese Laid-Open Patent Publication No. 2013-27912 discloses a technique that forms beads on the bottom wall of a hat-shaped product to reduce spring back.
According to the technique disclosed in Japanese Laid-Open Patent Publication No. 2009-255106, traces of embossing are difficult to erase after the embossed parts in the intermediate product are flattened. The technique is not suitable for products that require high dimensional accuracy such as separators of fuel cells.
According to the technique disclosed in Japanese Laid-Open Patent Publication No. 2013-27912, the beads are not flattened after the product is finished and thus remain in the product. Therefore, as in the above case, the technique is not suitable for products that require high dimensional accuracy such as separators of fuel cells.